Not so long ago, security managers thought the electric strikes or electromagnets on their doors, working in conjunction with their brand new card readers, were a tremendous improvement to their security systems. Imagine their horror in seeing that the door never closed once a valid presentation opened it.

Chivalry dictates that we hold the door for someone following us, and it is precisely that type of tradition that gives security managers nightmares. Electric strikes and magnets add to overall security, but many times one important link in the system is overlooked: the user.

User training and orientation programs are a must when implementing a new security system, but common courtesies can negate some or most benefits of modem card access control. Once a secured swinging or sliding door is open, it's easy to lose track of the number of people passing through and in which direction they're traveling.

A relatively new approach to controlled access combines the established environmental and aesthetic benefits of revolving doors with a traffic control function by including some form of verification system, typically a card reader. Whether it's a simple pushbutton behind a guard's desk or a sophisticated biometric system using door control communication with a host computer, the card reader/revolving door marriage has become the most frequent and cost-efficient means of controlling traffic into and out of an area.

The card access system handles the actual identification and verification of the user, but its use is limited beyond that point. Signals can be monitored showing that electric strikes were released or doors opened, but normal entrance systems cannot determine whether a person actually passed through.

This type of system can cause problems with attendance and record keeping functions, but more importantly it can also affect the life safety and evacuation plans should an emergency occur.

Here's a simple example: An employee says to his coworker, "I'm supposed to work Saturday, but I'd rather be fishing. I know you always work Saturdays, so I'll give you my card and you can clock me in and out." These situations do happen and cost your company.

This scenario highlights one of the benefits of the card access/revolving door system. Once the verification system has determined that an employee is supposed to be in a certain area at a certain time, the revolving door does the rest. The door prevents tailgating (following a valid person in the same direction or entering from the opposite direction on their presentation) and substantially decreases or eliminates piggybacking (passing through with the valid person).

The technology used to detect someone passing through the door varies among manufacturers, but most use pressure-sensitive floor mats and possibly some form of spatial or presence detection. Most doors are adaptable to any card access system and allow for card access in one or both directions, with free exit by pushing a button, activating a motion detector, or stepping on a mat.

Security revolving doors have several advantages over conventional turnstiles and other types of security entrances. Security revolving doors can be used in both directions at the same time, allowing better traffic flow. A single security revolving door can safely process as many as 800 to 1,000 people per hour in one direction, almost 2,000 total.

Another benefit of security revolving doors is they can actually verify passage. Unlike other types of entrances, when a revolving door has the user enclosed in the exterior walls it can verify whether that person actually passed through the door. If for some reason the person did not use or missed the opportunity, he or she can use the next available quadrant to verify his or her passage.

This enables the door control to communicate with antipassback card systems to verify passage. If an employee, John Doe, were to tell the guard he missed an entry, the guard could check a status printout and see that John Doe presented his card and someone did enter the building, raising the question: Why is John Doe asking to get in?

Another feature of security revolving doors concerns building code acceptance. Although some codes address noncollapsible turnstile use, most public entrances must collapse for emergency exit purposes. Collapsibility defeats security purposes unless the door is equipped with magnetic breakaway. This feature is accepted by all four code groups and releases only on loss of line power or when actuated by smoke, fire, or an emergency release switch located on the building interior near the door.

Code regulations require an adjacent swing door with any revolving door, and this is a prime place to direct handicapped or delivery traffic. Putting an electric strike on the adjacent swing door and installing a separate card reader permits only those specifically authorized to use that swing door -- people with wheelchairs, mail carts, or express deliveries -- to enter. You may have accountability problems as discussed earlier, but the exposure will be limited to several times a day instead of thousands. Authorized users should be instructed to watch the door until it's closed to ensure no unauthorized entries occur during their passage.

Most doors can also be used in a nonsecurity mode as a simple automatic entrance door in supervised lobbies and then automatically converted to security doors after hours and on weekends. This feature allows for important human interaction when necessary while still providing cost-efficient control of remote entrances or after-hours control.

Many government contractors are required to maintain high levels of security, and security revolving doors can provide that service efficiently. With a staffed station costing anywhere from $80,000 to $150,000 per year, this type of entry system can pay for itself in as little as six months.

The best application of a security revolving door is a small-diameter (6 feet to 6 feet 6 inches) four-wing door. The area within the door is small enough to deter piggybacking, and the door always looks the same.

Three-wing doors are available but not recommended, as their larger area can encourage piggybacking and their control logic is more complicated. The door's throat opening is also smaller, which may force users to pass in only one direction at a time as they yield the right of way to someone entering from the other direction.

Revolving door manufacturers also provide door status lights, audible tones, and voice warnings for additional user friendliness. Status lights inform users of a valid presentation, in addition to the card reader light. Typically, a card reader light only illuminates for a few seconds and is not active through a security violation. In applications where lights may be slow to respond or difficult to see, audible signals can augment normal status lights. Verbal prompting signals or warnings can also assist users with door operations.

Card reader locations can be determined by application and type of reader used. Insertion and swipe readers should be located near the door for convenience, whereas proximity readers should be mounted on pedestals away from the door to avoid multiple reads while passing through the door.

Card reader installers should look at traffic flows -- in hallways, around sharp corners, etc. -- before recommending reader locations. They should consult both reader and door manufacturers before determining final mounting locations.

It is also important to coordinate the installation of both card reader personnel and door installation personnel. This final point of system connection may result in several trips by both parties if they are unfamiliar with the other's system or lack coordination or wiring diagrams for each system.

In situations where increased levels of security are necessary and the luxury of slower traffic is possible, security portals or mantraps may be used. These entrances use similar verification devices along with multiple verifications for explosives and heavy metal detection.

These higher-degree procedures take additional time but are possible in lower traffic areas. You would not use a mantrap on a front entrance door, but you could use one at a research lab or computer room where traffic is limited or security needs are high.

For security entrances requiring barrier-free access, alternatives are available. The most common barrier-free security system used with a small-diameter security revolving door is an adjacent swing door with a low energy (slow) automatic operator. The swing door can be controlled by an electric lock and card access system, along with a remote camera.

Most manufacturers can customize logic or functional requirements to specific applications, so consult their expertise before finalizing design requirements and specifications.

About the Author . . .

Donald J. Haerer is product manager for the revolving door line of Horton Automatics in Corpus Christi, TX. He is a member of ASIS.

Reprinted from the November 1990 Special Section of Security' Management, American Society for Industrial Security, 1655 North Fort Myer Drive, Suite 1200, Arlington, VA 22209.